[linux.git] / security / commoncap.c

/* Common capabilities, needed by capability.o and root_plug.o 
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *
 */

#include <linux/capability.h>
#include <linux/config.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/security.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/smp_lock.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/ptrace.h>
#include <linux/xattr.h>
#include <linux/hugetlb.h>

int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
{
	NETLINK_CB(skb).eff_cap = current->cap_effective;
	return 0;
}

EXPORT_SYMBOL(cap_netlink_send);

int cap_netlink_recv(struct sk_buff *skb)
{
	if (!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN))
		return -EPERM;
	return 0;
}

EXPORT_SYMBOL(cap_netlink_recv);

int cap_capable (struct task_struct *tsk, int cap)
{
	/* Derived from include/linux/sched.h:capable. */
	if (cap_raised(tsk->cap_effective, cap))
		return 0;
	return -EPERM;
}

int cap_settime(struct timespec *ts, struct timezone *tz)
{
	if (!capable(CAP_SYS_TIME))
		return -EPERM;
	return 0;
}

int cap_ptrace (struct task_struct *parent, struct task_struct *child)
{
	/* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
	if (!cap_issubset (child->cap_permitted, current->cap_permitted) &&
	    !capable(CAP_SYS_PTRACE))
		return -EPERM;
	return 0;
}

int cap_capget (struct task_struct *target, kernel_cap_t *effective,
		kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
	/* Derived from kernel/capability.c:sys_capget. */
	*effective = cap_t (target->cap_effective);
	*inheritable = cap_t (target->cap_inheritable);
	*permitted = cap_t (target->cap_permitted);
	return 0;
}

int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
	/* Derived from kernel/capability.c:sys_capset. */
	/* verify restrictions on target's new Inheritable set */
	if (!cap_issubset (*inheritable,
			   cap_combine (target->cap_inheritable,
					current->cap_permitted))) {
		return -EPERM;
	}

	/* verify restrictions on target's new Permitted set */
	if (!cap_issubset (*permitted,
			   cap_combine (target->cap_permitted,
					current->cap_permitted))) {
		return -EPERM;
	}

	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
	if (!cap_issubset (*effective, *permitted)) {
		return -EPERM;
	}

	return 0;
}

void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
		     kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
	target->cap_effective = *effective;
	target->cap_inheritable = *inheritable;
	target->cap_permitted = *permitted;
}

int cap_bprm_set_security (struct linux_binprm *bprm)
{
	/* Copied from fs/exec.c:prepare_binprm. */

	/* We don't have VFS support for capabilities yet */
	cap_clear (bprm->cap_inheritable);
	cap_clear (bprm->cap_permitted);
	cap_clear (bprm->cap_effective);

	/*  To support inheritance of root-permissions and suid-root
	 *  executables under compatibility mode, we raise all three
	 *  capability sets for the file.
	 *
	 *  If only the real uid is 0, we only raise the inheritable
	 *  and permitted sets of the executable file.
	 */

	if (!issecure (SECURE_NOROOT)) {
		if (bprm->e_uid == 0 || current->uid == 0) {
			cap_set_full (bprm->cap_inheritable);
			cap_set_full (bprm->cap_permitted);
		}
		if (bprm->e_uid == 0)
			cap_set_full (bprm->cap_effective);
	}
	return 0;
}

void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
{
	/* Derived from fs/exec.c:compute_creds. */
	kernel_cap_t new_permitted, working;

	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
	working = cap_intersect (bprm->cap_inheritable,
				 current->cap_inheritable);
	new_permitted = cap_combine (new_permitted, working);

	if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
	    !cap_issubset (new_permitted, current->cap_permitted)) {
		current->mm->dumpable = suid_dumpable;

		if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
			if (!capable(CAP_SETUID)) {
				bprm->e_uid = current->uid;
				bprm->e_gid = current->gid;
			}
			if (!capable (CAP_SETPCAP)) {
				new_permitted = cap_intersect (new_permitted,
							current->cap_permitted);
			}
		}
	}

	current->suid = current->euid = current->fsuid = bprm->e_uid;
	current->sgid = current->egid = current->fsgid = bprm->e_gid;

	/* For init, we want to retain the capabilities set
	 * in the init_task struct. Thus we skip the usual
	 * capability rules */
	if (current->pid != 1) {
		current->cap_permitted = new_permitted;
		current->cap_effective =
		    cap_intersect (new_permitted, bprm->cap_effective);
	}

	/* AUD: Audit candidate if current->cap_effective is set */

	current->keep_capabilities = 0;
}

int cap_bprm_secureexec (struct linux_binprm *bprm)
{
	/* If/when this module is enhanced to incorporate capability
	   bits on files, the test below should be extended to also perform a 
	   test between the old and new capability sets.  For now,
	   it simply preserves the legacy decision algorithm used by
	   the old userland. */
	return (current->euid != current->uid ||
		current->egid != current->gid);
}

int cap_inode_setxattr(struct dentry *dentry, char *name, void *value,
		       size_t size, int flags)
{
	if (!strncmp(name, XATTR_SECURITY_PREFIX,
		     sizeof(XATTR_SECURITY_PREFIX) - 1)  &&
	    !capable(CAP_SYS_ADMIN))
		return -EPERM;
	return 0;
}

int cap_inode_removexattr(struct dentry *dentry, char *name)
{
	if (!strncmp(name, XATTR_SECURITY_PREFIX,
		     sizeof(XATTR_SECURITY_PREFIX) - 1)  &&
	    !capable(CAP_SYS_ADMIN))
		return -EPERM;
	return 0;
}

/* moved from kernel/sys.c. */
/* 
 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
 * a process after a call to setuid, setreuid, or setresuid.
 *
 *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
 *  {r,e,s}uid != 0, the permitted and effective capabilities are
 *  cleared.
 *
 *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
 *  capabilities of the process are cleared.
 *
 *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
 *  capabilities are set to the permitted capabilities.
 *
 *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
 *  never happen.
 *
 *  -astor 
 *
 * cevans - New behaviour, Oct '99
 * A process may, via prctl(), elect to keep its capabilities when it
 * calls setuid() and switches away from uid==0. Both permitted and
 * effective sets will be retained.
 * Without this change, it was impossible for a daemon to drop only some
 * of its privilege. The call to setuid(!=0) would drop all privileges!
 * Keeping uid 0 is not an option because uid 0 owns too many vital
 * files..
 * Thanks to Olaf Kirch and Peter Benie for spotting this.
 */
static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
					int old_suid)
{
	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
	    !current->keep_capabilities) {
		cap_clear (current->cap_permitted);
		cap_clear (current->cap_effective);
	}
	if (old_euid == 0 && current->euid != 0) {
		cap_clear (current->cap_effective);
	}
	if (old_euid != 0 && current->euid == 0) {
		current->cap_effective = current->cap_permitted;
	}
}

int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
			  int flags)
{
	switch (flags) {
	case LSM_SETID_RE:
	case LSM_SETID_ID:
	case LSM_SETID_RES:
		/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
		if (!issecure (SECURE_NO_SETUID_FIXUP)) {
			cap_emulate_setxuid (old_ruid, old_euid, old_suid);
		}
		break;
	case LSM_SETID_FS:
		{
			uid_t old_fsuid = old_ruid;

			/* Copied from kernel/sys.c:setfsuid. */

			/*
			 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
			 *          if not, we might be a bit too harsh here.
			 */

			if (!issecure (SECURE_NO_SETUID_FIXUP)) {
				if (old_fsuid == 0 && current->fsuid != 0) {
					cap_t (current->cap_effective) &=
					    ~CAP_FS_MASK;
				}
				if (old_fsuid != 0 && current->fsuid == 0) {
					cap_t (current->cap_effective) |=
					    (cap_t (current->cap_permitted) &
					     CAP_FS_MASK);
				}
			}
			break;
		}
	default:
		return -EINVAL;
	}

	return 0;
}

void cap_task_reparent_to_init (struct task_struct *p)
{
	p->cap_effective = CAP_INIT_EFF_SET;
	p->cap_inheritable = CAP_INIT_INH_SET;
	p->cap_permitted = CAP_FULL_SET;
	p->keep_capabilities = 0;
	return;
}

int cap_syslog (int type)
{
	if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
		return -EPERM;
	return 0;
}

int cap_vm_enough_memory(long pages)
{
	int cap_sys_admin = 0;

	if (cap_capable(current, CAP_SYS_ADMIN) == 0)
		cap_sys_admin = 1;
	return __vm_enough_memory(pages, cap_sys_admin);
}

EXPORT_SYMBOL(cap_capable);
EXPORT_SYMBOL(cap_settime);
EXPORT_SYMBOL(cap_ptrace);
EXPORT_SYMBOL(cap_capget);
EXPORT_SYMBOL(cap_capset_check);
EXPORT_SYMBOL(cap_capset_set);
EXPORT_SYMBOL(cap_bprm_set_security);
EXPORT_SYMBOL(cap_bprm_apply_creds);
EXPORT_SYMBOL(cap_bprm_secureexec);
EXPORT_SYMBOL(cap_inode_setxattr);
EXPORT_SYMBOL(cap_inode_removexattr);
EXPORT_SYMBOL(cap_task_post_setuid);
EXPORT_SYMBOL(cap_task_reparent_to_init);
EXPORT_SYMBOL(cap_syslog);
EXPORT_SYMBOL(cap_vm_enough_memory);

MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
MODULE_LICENSE("GPL");
Commit	Line	Data
1da177e4 LT	1	/* Common capabilities, needed by capability.o and root_plug.o
	2	*
	3	* This program is free software; you can redistribute it and/or modify
	4	* it under the terms of the GNU General Public License as published by
	5	* the Free Software Foundation; either version 2 of the License, or
	6	* (at your option) any later version.
	7	*
	8	*/
	9
c59ede7b	10	#include <linux/capability.h>
1da177e4 LT	11	#include <linux/config.h>
	12	#include <linux/module.h>
	13	#include <linux/init.h>
	14	#include <linux/kernel.h>
	15	#include <linux/security.h>
	16	#include <linux/file.h>
	17	#include <linux/mm.h>
	18	#include <linux/mman.h>
	19	#include <linux/pagemap.h>
	20	#include <linux/swap.h>
	21	#include <linux/smp_lock.h>
	22	#include <linux/skbuff.h>
	23	#include <linux/netlink.h>
	24	#include <linux/ptrace.h>
	25	#include <linux/xattr.h>
	26	#include <linux/hugetlb.h>
	27
	28	int cap_netlink_send(struct sock sk, struct sk_buff skb)
	29	{
	30	NETLINK_CB(skb).eff_cap = current->cap_effective;
	31	return 0;
	32	}
	33
	34	EXPORT_SYMBOL(cap_netlink_send);
	35
	36	int cap_netlink_recv(struct sk_buff *skb)
	37	{
	38	if (!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN))
	39	return -EPERM;
	40	return 0;
	41	}
	42
	43	EXPORT_SYMBOL(cap_netlink_recv);
	44
	45	int cap_capable (struct task_struct *tsk, int cap)
	46	{
	47	/* Derived from include/linux/sched.h:capable. */
	48	if (cap_raised(tsk->cap_effective, cap))
	49	return 0;
	50	return -EPERM;
	51	}
	52
	53	int cap_settime(struct timespec ts, struct timezone tz)
	54	{
	55	if (!capable(CAP_SYS_TIME))
	56	return -EPERM;
	57	return 0;
	58	}
	59
	60	int cap_ptrace (struct task_struct parent, struct task_struct child)
	61	{
	62	/* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
	63	if (!cap_issubset (child->cap_permitted, current->cap_permitted) &&
	64	!capable(CAP_SYS_PTRACE))
	65	return -EPERM;
	66	return 0;
	67	}
	68
	69	int cap_capget (struct task_struct target, kernel_cap_t effective,
	70	kernel_cap_t inheritable, kernel_cap_t permitted)
	71	{
	72	/* Derived from kernel/capability.c:sys_capget. */
	73	*effective = cap_t (target->cap_effective);
	74	*inheritable = cap_t (target->cap_inheritable);
75	*permitted = cap_t (target->cap_permitted);
76	return 0;
77	}
78
79	int cap_capset_check (struct task_struct target, kernel_cap_t effective,
80	kernel_cap_t inheritable, kernel_cap_t permitted)
81	{
82	/* Derived from kernel/capability.c:sys_capset. */
83	/* verify restrictions on target's new Inheritable set */
84	if (!cap_issubset (*inheritable,
85	cap_combine (target->cap_inheritable,
86	current->cap_permitted))) {
87	return -EPERM;
88	}
89
90	/* verify restrictions on target's new Permitted set */
91	if (!cap_issubset (*permitted,
92	cap_combine (target->cap_permitted,
93	current->cap_permitted))) {
94	return -EPERM;
95	}
96
97	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
98	if (!cap_issubset (effective, permitted)) {
99	return -EPERM;
100	}
101
102	return 0;
103	}
104
105	void cap_capset_set (struct task_struct target, kernel_cap_t effective,
106	kernel_cap_t inheritable, kernel_cap_t permitted)
107	{
108	target->cap_effective = *effective;
109	target->cap_inheritable = *inheritable;
110	target->cap_permitted = *permitted;
111	}
112
113	int cap_bprm_set_security (struct linux_binprm *bprm)
114	{
115	/* Copied from fs/exec.c:prepare_binprm. */
116
117	/* We don't have VFS support for capabilities yet */
118	cap_clear (bprm->cap_inheritable);
119	cap_clear (bprm->cap_permitted);
120	cap_clear (bprm->cap_effective);
121
122	/* To support inheritance of root-permissions and suid-root
123	* executables under compatibility mode, we raise all three
124	* capability sets for the file.
125	*
126	* If only the real uid is 0, we only raise the inheritable
127	* and permitted sets of the executable file.
128	*/
129
130	if (!issecure (SECURE_NOROOT)) {
131	if (bprm->e_uid == 0 \|\| current->uid == 0) {
132	cap_set_full (bprm->cap_inheritable);
133	cap_set_full (bprm->cap_permitted);
134	}
135	if (bprm->e_uid == 0)
136	cap_set_full (bprm->cap_effective);
137	}
138	return 0;
139	}
140
141	void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
142	{
143	/* Derived from fs/exec.c:compute_creds. */
144	kernel_cap_t new_permitted, working;
145
146	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
147	working = cap_intersect (bprm->cap_inheritable,
148	current->cap_inheritable);
149	new_permitted = cap_combine (new_permitted, working);
150
151	if (bprm->e_uid != current->uid \|\| bprm->e_gid != current->gid \|\|
152	!cap_issubset (new_permitted, current->cap_permitted)) {
d6e71144	153	current->mm->dumpable = suid_dumpable;
1da177e4 LT	154
	155	if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
	156	if (!capable(CAP_SETUID)) {
	157	bprm->e_uid = current->uid;
	158	bprm->e_gid = current->gid;
	159	}
	160	if (!capable (CAP_SETPCAP)) {
	161	new_permitted = cap_intersect (new_permitted,
	162	current->cap_permitted);
	163	}
	164	}
	165	}
	166
	167	current->suid = current->euid = current->fsuid = bprm->e_uid;
	168	current->sgid = current->egid = current->fsgid = bprm->e_gid;
	169
	170	/* For init, we want to retain the capabilities set
	171	* in the init_task struct. Thus we skip the usual
	172	* capability rules */
	173	if (current->pid != 1) {
	174	current->cap_permitted = new_permitted;
	175	current->cap_effective =
	176	cap_intersect (new_permitted, bprm->cap_effective);
	177	}
	178
	179	/* AUD: Audit candidate if current->cap_effective is set */
	180
	181	current->keep_capabilities = 0;
	182	}
	183
	184	int cap_bprm_secureexec (struct linux_binprm *bprm)
	185	{
	186	/* If/when this module is enhanced to incorporate capability
	187	bits on files, the test below should be extended to also perform a
	188	test between the old and new capability sets. For now,
	189	it simply preserves the legacy decision algorithm used by
	190	the old userland. */
	191	return (current->euid != current->uid \|\|
	192	current->egid != current->gid);
	193	}
	194
	195	int cap_inode_setxattr(struct dentry dentry, char name, void *value,
	196	size_t size, int flags)
	197	{
	198	if (!strncmp(name, XATTR_SECURITY_PREFIX,
	199	sizeof(XATTR_SECURITY_PREFIX) - 1) &&
	200	!capable(CAP_SYS_ADMIN))
	201	return -EPERM;
	202	return 0;
	203	}
	204
	205	int cap_inode_removexattr(struct dentry dentry, char name)
	206	{
	207	if (!strncmp(name, XATTR_SECURITY_PREFIX,
	208	sizeof(XATTR_SECURITY_PREFIX) - 1) &&
	209	!capable(CAP_SYS_ADMIN))
	210	return -EPERM;
	211	return 0;
	212	}
	213
	214	/* moved from kernel/sys.c. */
	215	/*
	216	* cap_emulate_setxuid() fixes the effective / permitted capabilities of
	217	* a process after a call to setuid, setreuid, or setresuid.
218	*
219	* 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
220	* {r,e,s}uid != 0, the permitted and effective capabilities are
221	* cleared.
222	*
223	* 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
224	* capabilities of the process are cleared.
225	*
226	* 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
227	* capabilities are set to the permitted capabilities.
228	*
229	* fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
230	* never happen.
231	*
232	* -astor
233	*
234	* cevans - New behaviour, Oct '99
235	* A process may, via prctl(), elect to keep its capabilities when it
236	* calls setuid() and switches away from uid==0. Both permitted and
237	* effective sets will be retained.
238	* Without this change, it was impossible for a daemon to drop only some
239	* of its privilege. The call to setuid(!=0) would drop all privileges!
240	* Keeping uid 0 is not an option because uid 0 owns too many vital
241	* files..
242	* Thanks to Olaf Kirch and Peter Benie for spotting this.
243	*/
244	static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
245	int old_suid)
246	{
247	if ((old_ruid == 0 \|\| old_euid == 0 \|\| old_suid == 0) &&
248	(current->uid != 0 && current->euid != 0 && current->suid != 0) &&
249	!current->keep_capabilities) {
250	cap_clear (current->cap_permitted);
251	cap_clear (current->cap_effective);
252	}
253	if (old_euid == 0 && current->euid != 0) {
254	cap_clear (current->cap_effective);
255	}
256	if (old_euid != 0 && current->euid == 0) {
257	current->cap_effective = current->cap_permitted;
258	}
259	}
260
261	int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
262	int flags)
263	{
264	switch (flags) {
265	case LSM_SETID_RE:
266	case LSM_SETID_ID:
267	case LSM_SETID_RES:
268	/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
269	if (!issecure (SECURE_NO_SETUID_FIXUP)) {
270	cap_emulate_setxuid (old_ruid, old_euid, old_suid);
271	}
272	break;
273	case LSM_SETID_FS:
274	{
275	uid_t old_fsuid = old_ruid;
276
277	/* Copied from kernel/sys.c:setfsuid. */
278
279	/*
280	* FIXME - is fsuser used for all CAP_FS_MASK capabilities?
281	* if not, we might be a bit too harsh here.
282	*/
283
284	if (!issecure (SECURE_NO_SETUID_FIXUP)) {
285	if (old_fsuid == 0 && current->fsuid != 0) {
286	cap_t (current->cap_effective) &=
287	~CAP_FS_MASK;
288	}
289	if (old_fsuid != 0 && current->fsuid == 0) {
290	cap_t (current->cap_effective) \|=
291	(cap_t (current->cap_permitted) &
292	CAP_FS_MASK);
293	}
294	}
295	break;
296	}
297	default:
298	return -EINVAL;
299	}
300
301	return 0;
302	}
303
304	void cap_task_reparent_to_init (struct task_struct *p)
305	{
306	p->cap_effective = CAP_INIT_EFF_SET;
307	p->cap_inheritable = CAP_INIT_INH_SET;
308	p->cap_permitted = CAP_FULL_SET;
309	p->keep_capabilities = 0;
310	return;
311	}
312
313	int cap_syslog (int type)
314	{
315	if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
316	return -EPERM;
317	return 0;
318	}
319
320	int cap_vm_enough_memory(long pages)
321	{
322	int cap_sys_admin = 0;
323
324	if (cap_capable(current, CAP_SYS_ADMIN) == 0)
325	cap_sys_admin = 1;
326	return __vm_enough_memory(pages, cap_sys_admin);
327	}
328
329	EXPORT_SYMBOL(cap_capable);
330	EXPORT_SYMBOL(cap_settime);
331	EXPORT_SYMBOL(cap_ptrace);
332	EXPORT_SYMBOL(cap_capget);
333	EXPORT_SYMBOL(cap_capset_check);
334	EXPORT_SYMBOL(cap_capset_set);
335	EXPORT_SYMBOL(cap_bprm_set_security);
336	EXPORT_SYMBOL(cap_bprm_apply_creds);
337	EXPORT_SYMBOL(cap_bprm_secureexec);
338	EXPORT_SYMBOL(cap_inode_setxattr);
339	EXPORT_SYMBOL(cap_inode_removexattr);
340	EXPORT_SYMBOL(cap_task_post_setuid);
341	EXPORT_SYMBOL(cap_task_reparent_to_init);
342	EXPORT_SYMBOL(cap_syslog);
343	EXPORT_SYMBOL(cap_vm_enough_memory);
344
345	MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
346	MODULE_LICENSE("GPL");